Sunday, May 21, 2017

Which is the smoothest ride - rod or rail?

For the first time, the TARC rules state that the top 100 contestants making it to the Nationals cannot use a rod; however, they can practice and qualify using one. It's difficult enough to achieve a good score with all the variables associated with the rocket, so I can greatly sympathize with any team showing up at Manassas that qualified with their rocket being launched from a standard 1/4" rod. Yes, they can add rail buttons and practice in the month between final score submission and Nationals, but what effect will this change have on the flight performance? Does a rail exert more friction on the rocket than the rod, thereby causing a loss of altitude and cancelling the benefit of its increased rigidity? Or is the rod, with its well known "rod whip", going to cost the model even more altitude? It's important I find out, because a couple of my designs for this year's Geezer TARC barely make the goal with the optimum motor configurations for deployment at apogee, and I need to know if I can go with these motor combos. Duane attributes his loss last year to rail friction (his model was a couple of hundred feet low), and I have no desire to follow in those footsteps.

Here are a couple things I do know:
  • No simulation program - Open Rocket, RockSim, SpaceCad, etc - takes into account the friction generated as the rocket slides up the rail or rod. These codes can roughly account for the atmospheric drag of the lug or rail buttons as the model progresses through its trajectory, but assume that the rod or rail is frictionless, which ain't realistic.
  • Calculations done by Tim Van Milligan at Apogee Rockets indicate that rail buttons are more draggy than launch lugs, especially if the lugs are fairly long, and have had their ends modified. So there is going to be a performance hit even if the rod and rail exert the same friction, leaving open the question of whether the simulation programs can model this properly (lugs are in the codes, but rail buttons have to be "kludged").
The above are not very helpful in providing the numbers I need. That means I need to collect data - which means an experiment is in order. After a little thought, I have devised the following scheme:
  • Construct a mid power rocket - must be a decent size so that the rail buttons/launch lug do not dominate the drag. It turns out I have the perfect kit - the Balsa Machining 3" School Rocket, which has a pre-slotted 3' diameter tube, laser cut balsa fins, and a nice plastic nose cone that will reduce the amount of time spent finishing the model. All I need to do is add a payload section to hold an altimeter, plus replace the 24 mm motor mount with a 29 mm to provide some needed power.
  • Launch the above model several times, alternating between rod and rail pads. Both the rod and rail should be as close to vertical as I can make them, and the launches should be dome quickly, with little time separation. This will minimize the effects of changing weather. Each set of two launches (rod and rail) should be done with motors from the same pack or batch to reduce motor variations. What I am looking for is a trend among the flight altitudes, with either the rail or rod producing consistently lower altitudes. If there is no such trend, I need to try to evaluate whether something is messing with my experiment; if not, then the conclusion is that it doesn't make much difference which type of pad you use.
Here is a screenshot of the OpenRocket design of the modified School Rocket, which I call the GDTV-1 (Guidance Drag Test Vehicle #1). I have already started cutting tubes and have ordered the rail buttons in anticipation of performing the experiment at this year's Southern Thunder (June 24/25). Pegasus Field is already overgrown, so I doubt we will be launching there much until it is mowed in the Fall. This will force me to attend the club launches in Manchester if I want to fly every month.
The GDTV-1 (Click to enlarge).

Sunday, May 14, 2017

The 2018 Geezer TARC season begins...

Now that the rules have been released for the 2018 TARC competition, we can start the annual Geezer TARC contest. Here are the rules for 2018:

The rules are the same as those for the 2018 TARC challenge with the following exceptions:

  • Geezer TARC begins with the announcement of the 2018 rules in May (which happened today) and ends with the contestants’ rockets being launched at a single event (date TBD, probably on a Saturday on or near the start of the college football season).
  • The rockets must launch off standard rails; the use of launchers with rods will not be permitted (as per the 2018 Nationals).
  • Each contestant may enter up to two rockets. These rockets may not fly before the official launch date, and the score shall be determined by the first flight of each on that date. The contestant's score shall be the better of the two flights, or the score of one flight if only one rocket is entered.
  • Breaking with previous Geezer TARC contests, contestants must use one of the regulation TARC altimeters (APRA, PNUT, or Firefly) as the "official" measure of altitude. A re-flight will be allowed in the event of an altimeter malfunction, provided the flyer can demonstrate it was not his or her fault (i.e., did not forget to turn it on or provide vent holes to the outside). As per the 2018 rules, the altimeter used to record altitude may be used for no other purpose, though the use of a Jolly Logic Chute Release or other altimeter type is permitted for flight control.
  • There is only one rocket per design, and there are no test or sub-scale flights permitted for the design. Its merit will be judged solely by the rocket’s performance at the contest launch. If two rockets are entered, they must be of substantially different design - different number of motors, fins, or something major - an inch shorter or taller does not constitute a substantial difference, nor does the same design at a different scale (which will be very hard to do this year with the restrictions on the body tube diameters).
And so it begins... May the odds ever be in your favor!

A little launching...

Late April/early May can be a busy time for HARA, with schools requesting rocket assistance/demos for their Space Week activities.  Our club VP and his wife did an outstanding job with "Build it/Fly it" sessions at a couple of local schools, and Duane got tapped with performing the annual rocket demo at Horizon Elementary. Despite the small field, I love the event at Horizon - the enthusiasm of the kids is terrific - so I volunteered to assist in the Thursday afternoon launch. It also gave me an excuse to take part of a day off work, which ain't a bad thing these days.

Duane loads his School Rocket as the Horizon students file in on the north side of the field (Click to enlarge).
We arrived at the school around 1, set up Duane's pads and controller, and unpacked the rockets. Each of us had brought 3 - I followed a school theme with my Estes Pink Crayon (B6-4), Skywriter (A8-3), and Generic (A8-3), whereas Duane had prepped his Odd'l Rockets Birdie (A10-3T), Estes Make It Take It (A8-3), and BMS 3" School Rocket (D12-3). The Launch Control Officer (LCO) for the demo would be Beth Bero, an outstanding Horizon teacher who is into science stuff. She must have been a lucky LCO, for we dd not loose any of the 6 rockets launched, and there was only one minor flight deviation when the nose cone of the School Rocket separated from the rest of the model at ejection. A post-flight check showed that the plastic attach point for the shock cord had broken - sometimes these plastic nose cones need a bit of reinforcing to enable them to withstand the stresses at ejection.

Beth sends the Estes Skywriter on its way (Click to enlarge).
The important thing is that the 700 kids present enjoyed the launch. My thanks to our two rocket retrievers, Cricket and Jason, who did a fabulous job recovering the birds. I am looking forward to next year, and am thinking that it is time to build a mid-power saucer so that we can awe the young ones with the fire and noise of F composite motors. Duane suggests that it would also be a good idea to throw some kits Beth's way, so that the Horizon students can see their rockets launched in the demo. This would most definitely add to the fun.

Starting to set up the range at the Manchester sod farm (Click to enlarge).
HARA's regularly-scheduled club launch had to be scrubbed on May 6 due to high winds, so it was rescheduled for yesterday. Being a low power dude, I normally do not attend Manchester launches, as 2 hours is a pretty long ride to launch some mod rocs, especially with Pegasus field just a few blocks away. However, I was in the mood to launch some mid-power rockets, so I grabbed my Estes Trajector and Majestic and hitched a ride with Duane up to the sod farm. We arrived around 9:30, just as the clouds were making way for the Sun, and joined in with setting up the range, which opened around 10:30 or so. The crowd was light, as is the norm with make up launches; I estimate that about 60 rockets were launched on Saturday, at a very leisurely pace.

My Trajector is first off the pad on an Estes F15
(Click to enlarge).
And the first to drift into the trees (Click to enlarge).
Even though the skies were rapidly clearing, the wind was still high, in excess of 10 miles per hour out of the north. Due to sod operations, the operators of the farm had situated us on the southwest side of the field, the worst place to be given the wind situation. Needless to say, the rocket gods were very pleased with the number of sacrifices Saturday, and many a bird drifted into the trees to the west and south of our launch position. The first of these happened to be the first rocket launched - my Trajector, on a F15-6. It started out well, with a good straight boost towards the north east, but the rocket stayed aloft too long in the high wind, drifting into the top of a tree near the edge of the field. It hung there, 60 feet off the ground, mocking me throughout the day. Angling the rods and rails helped a bit, but thermals begin to kick in as the day wore on; the crowd spent several minutes watching a mod roc cycle between descending, hanging stationary, and ascending before it finally decided to drift into the trees. It was a tough day for many of the flyers - fortunately, Chris Short was there with his trailer of goodies, enabling rocketeers to purchase kits and motors to replace their losses (or to add to the collection).

Art shoulders his Level 1 rocket for its journey out to the pad (Click to enlarge).
On the high-power side, there were a couple of level 1 certification attempts, one by a University of Alabama in Huntsville (UAH) student. He was very happy to cert level 1 with his black homemade carbon-fiber rocket powered by an Aerotech H motor. Art Woodling's old red-white-and-blue level 1 rocket put in an outstanding performance on an Aerotech I; it even managed to land within the field, thanks in part to a Jolly Logic Chute Release. A UAH rocket team flew a prototype rocket twice on J motors; it featured a deployable glider in a canister, which failed to deploy on both flights. We have had several college teams try deployable gliders in the NASA Student Launch program over the years, most of which have ended in failure. It is very tough to design and build a canister that will cleanly eject from the rocket's interior and then separate to allow the glider to deploy properly. Anyway, the first flight of the UAH rocket landed in the field, whereas the second saw it drifting well beyond the southern treeline. I do not know if it became an expensive sacrifice to the rocket gods, because Duane and I had to leave before the team returned from the recovery attempt.

A member of the UAH rocket team discusses their rocket with Art (Click to enlarge).
Another Manchester launch is now in the books - flew one, lost it. Fortunately, Estes now has the Trajector on sale for 16 bucks, so I'm not out much (unless you count the money I gave Chris Short for an Aerotech Arreaux - I gotta learn to stay out of his trailer of goodies).

Saturday, May 13, 2017

The pad's on fire!

Last Saturday Duane and I joined members of Liberty Middle School's TARC team at Pegasus field for an end-of-year celebratory fun launch. The day was sunny, albeit quite breezy - most of the rockets drifted much farther downwind than they travelled up. Despite the wind, there were quite a number of students and parents present for the launch, which featured the 3 inch diameter Balsa Machining Service School Rockets (an awesome deal, btw) built by the team earlier in the year, along with a few Estes rockets. Liberty brought the rockets and motors, and it was up to me and Duane to furnish the launch gear. We were prepared - I set up my trusty camera tripod launcher and unpacked my Pro Series launch controller while Duane placed his two Tilt-A-Pad clones (1/8" and 3/16" rods) next to the clips of his very nice home-brew controller.

Liberty Middle's TARC team gets ready to start their last launch of the school year (Click to enlarge).
The first School Rocket's flight went without a hitch - straight up on an Estes E9, with a soft landing a considerable distance downwind from the pad. However, the E9 motor in the second model, which was poised atop my pad, completely blew out the nozzle upon ignition. As the rocket sat motionless amid an expanding cloud of smoke, hot propellant flowed freely from the bottom, catching both the rocket and my pad - namely the plastic top of the camera tripod underneath the blast deflector - on fire. It took us a few minutes to extinguish the flames, and I stared mournfully at the melted part of my pad; the deflector will obviously have to be replaced, and I may have to do the same for the tripod  head as well. The bottom of the School Rocket was severely burned, but enough was left of the fins and motor mount to enable it to make a safe and stable flight a few minutes later. That rocket was one tough hombre!

Did I mention that I am beginning to hate Estes E motors?

Smoke billows from the burning pad and
School Rocket (Click to enlarge).
Aftermath: The top of my pad (Click to enlarge).
Aftermath: The bottom of the School Rocket
(Click to enlarge).
The scorched School Rocket takes flight
(Click to enlarge).
The rest of the launch went pretty well, with the only loss being a Quest Nike Smoke, which drifted way out of the field to be lost somewhere in the high grass - the combination of C motors in small rockets and a windy day is not a good one. There were some nice flights, including those of an Estes Black Star Voyager and a Renegade-D, both of which landed within the field. Duane and I left Pegasus around 2 and headed to the U.S. Space and Rocket Center, where we helped Vince set up a small rocket display outside the Space Station simulation area. We chatted rockets with the passers-by for about 3 hours before packing up for home.

Lift off of an Estes Black Star Voyager
(Click to enlarge).
And the crowd watches it descend under chute
(Click to enlarge).
A Liberty team member hooks up an Estes Patriot
(Click to enlarge).
The Renegade-D gets going (Click to enlarge).
All in all, a good day - now to make repairs to my launch pad. I'm wondering if I should insist that all Estes E motors launch off someone else's from now on. It seems the safe thing to do...

Vince mans the display at the USSRC (Click to enlarge).

Sunday, April 30, 2017

Fixing a broken bunny...

Every rocket suffers battle scars during its lifetime; dings, nicks, chipped paint, and torn decals are the proud badges of many flights. Most of these are easily touched up with a dab of paint or the judicious use of markers, but sometimes the damage is more than a slight nick on a fin - sometimes it is severe enough to warrant considering scrapping the model. Such was the case with two of mine, which were damaged so badly that they sat in the repair box for years, dolefully waiting for me to decide their fate.

The first of these was my clone of the Centuri MX-774. Its first - and only - flight was at a Manchester launch about 5 years ago. The rocket achieved a decent altitude on a A8-3, but was unlucky enough to land on a gravel area near the barn. The wind caught the streamer, dragging the model a considerable distance across the ground. Gravel and balsa, like asphalt and balsa, don't mix very well - the MX-774's nose cone was badly dinged and scraped, and a huge chunk was ripped out of one fin. Upon my return home, I deposited the model in the repair box, fully intending to build another. However, the years wore on, and my skills advanced to the point where I thought I may be able to repair the rocket.

My MX-774 clone before its ill-fated flight
(Click to enlarge).
So I sanded down the nose, applied Fill N Finish to the damaged areas and repainted. This repair of the nose cone was the easy part; I still had to deal with the torn fin. I used my hobby knife to carve the missing section into a small rectangle, into which I glued a piece of sealed and primered balsa. It worked better than I expected - a little sanding with sandpaper glued to a popsicle stick and some black paint resulted in a very decent repair. The nicked decals were touched up with a marker, et voila! Repair done, rocket returned to the fleet.

The pieces of my Cloud Hopper clone (Click to enlarge).
My Estes Cloud Hopper clone was next. It had suffered damage at the hands of some enthusiastic youngsters at Horizon Elementary School back in April of 2014 - being over eager to recover the model, they accidentally shattered one of the top wings and the winglet. My poor bunny rocket lay in the repair box for 3 years until I finally glued various pieces back together, applied Fill N Finish to the seams, did a bit of sanding, and repainted. It also turned out pretty well; the Cloud Hopper is once again ready to leap off the pad.

The repaired MX-774 and Cloud Hopper (Click to enlarge).

Been doing a lot of work travel this month, so I haven't had much time for the hobby. Still, I managed to finish an Estes Alpha (1970's decor) and a clone of the MRC Firefighter. I also have gathered all the parts needed to build a clone of the Estes Falcon Commander, which I hope to start this weekend. The build pace may have slowed, but it hasn't stopped.

Monday, April 3, 2017

Crossing the finish line...

Hope Rising starts Headhunter on another flight (Click to enlarge).
"It was the best of times, it was the worst of times..."

These words from Dicken's A Tale of Two Cities apply to so much of life, including TARC. The best of times - the Hope Rising team winning the University of North Alabama regional event with a 16 score, topping even the TARC world champions of a couple of years ago, Russellville. Or the Buckhorn Gold team scoring a extremely respectable 7 on their very first qualification flight.  Or Liberty Middle's Team Bazinga scoring 17 and 18 in back-to-back qualification flights. The worst of times - the sustainer of Fort Payne Elite's 4th rocket drifting into the trees, experiencing the same fate as its predecessors. Or the Falcon Rocketeers' rocket suffering through yet another destructive CATO involving a reloadable motor.  Or Buckhorn Gold's rocket dragging the launch controller wires up with it on their second qualification flight, resulting in a loss of 90 feet in altitude and a dismal score. This TARC season, like those of the past, saw many highs and lows. Many teams didn't think they would ever get a decent flight, while others struggled with achieving consistent results. Some teams performed 30, 40, even 50 practice flights; others only 5 or 6. However, no matter how much they practiced, all achieved the most important goal of TARC - they qualified.

They crossed the finish line...

Every year, after the qualification scores are turned in, I am inevitably confronted with the same comment - "My team worked so hard. We should have had a couple of good scores, but because of <motor variability, weather, or other reason>, we didn't. Do you think that's fair?"


TARC is like a race or other sporting event - you prepare, practice, and get your team ready for the big event. Lots of preparation and practice correlates with winning, but it does not guarantee it.  There are other factors that determine the outcome, some of which are beyond the team's control. Winning is desirable, but the most important thing is that you hung in there, giving it your all until the last score is turned in. A TARC team that does that is a winner, regardless of their final standing. The submission of 3 qual scores, no matter their values, is cause for celebration. The race has been run, the finish line crossed - no one can ask for more. The TARC teams in this area did great!

Congrats to the Falcon Rocketeers, Jurassic TARC, Hope Rising, James Clemens Team #1, Liberty Team Bazinga, the Fort Payne Elite, Buckhorn Team Blue, and Buckhorn Team Gold! See you on the field next season!

The Buckhorn teams prepare their blue and gold rockets (Click to enlarge).
The James Clemens team activates their rocket's altimeter (Click to enlarge).
Two of the Falcon Rocketeers load their rocket on the pad (Click to enlarge).
The ladies of Jurassic TARC get ready for another qualification attempt (Click to enlarge).
A Liberty Middle team member gives their rocket the final once-over before flight (Click to enlarge).

Monday, March 27, 2017

An afternoon with the Fort Payne Elite...

The Fort Payne Elite TARC team (Click to enlarge).
Yesterday, Duane and I took a little road trip to the tiny town of Fyffe up on Sand Mountain. Once there, we were supposed to link up with the Fort Payne Elite TARC team, one of three teams sponsored by Fort Payne High School. I had been working with them - by email - on the design and building of their rocket, and yesterday was slated to be qualification day. I was excited to meet the team for the first time, and Duane was his usual enthusiastic self about all things TARC. Plus, it got us out of town, which ain't a bad thing.

We arrived at the field right on schedule at 2 PM, and were joined by the team's supervising teacher and the teens within just a few minutes. Equipment was hauled out and carried over the wet and muddy ground to the launch site, in the southwest part of a nice cleared area. During the course of setting up, we learned that the TARC team's last practice flight had not gone well; the rocket drifted past the tree line and was lost in the woods on the north side of the field. Undaunted, the team put together a new rocket from available parts in a single evening, and it looked ready to fly.

A Fort Payne rocket awaits launch in this near sunset picture taken by
one of the team members (Click to enlarge).
Or so we thought. After setting up the pad, we discovered that the lower launch lug was misaligned - the stand off was not quite thick enough, so the team members cobbled together a new launch lug stand off for the lower section by epoxying some thin mixing sticks to the existing piece. This worked perfectly, with the model sliding easily along the rod. This left only the wind to contend with - my Kestrel showed an average speed of just over 9 mph, with gusts up to 16 mph. I did a little math and figured that the rocket had a good chance of drifting out of the field if launch was not performed during one of the increasingly rare lulls.

This Fort Payne team had an unusual trait - they were actually well organized, prepping the rocket quite efficiently and even putting tools away in the proper place, which floored Duane. He keeps bickering at his teams to do just that, and I was amused to find the 'benevolent dictator' speechless. Anyway, the rocket was loaded with an Aerotech E30 and placed on the pad. The igniter leads were hooked up, the launch controller connected to the battery, and everyone waited for the right moment. When it came, the Fort Payne rocket shot off the pad like a bullet, heading up into the blue sky. The parachutes deployed a little before apogee, and I immediately began wishing I was not so good at math. Sure enough, both parts of the rocket - egg capsule and sustainer - were drifting towards the tree line at a brisk pace. The sustainer landed in the top of a tree, about 60 feet up - definitely not recoverable. The egg capsule landed in the lower branches of a tree at the edge of the field, and it was retrieved by much use of a long stick.

The team loads the rocket on the pad (Click to enlarge).Leaving the rod on an E30 (Click to enlarge).
It was a pretty demoralizing setback, but the team was heartened a little bit by the flight stats - 730 feet peak altitude and down in 42 seconds. Perfect on the time, and just 45 feet shy of the altitude mark. Not bad for a first flight, and I was pleased to see them decide to build a new model and make another go of it later this week. That's pretty decent dedication, given that this is spring break for their school system. Not many kids would be messing around with rockets when they could be out goofing off, or, in the case of their teacher, on vacation. I hope the rocket gods smile on their qualification flights this coming weekend.